Originally Posted by Nomercy448

What’s the thickness of your brass? That’s really the culprit in the 350 Legend debacle - Win made chambers too small for the corresponding max bullet diameter to allow “normal” case neck thickness.
So if you figure 2 thou neck tension, your math becomes: .357 + 2 x neck thickness - 0.002 = finished round dia, which has to be a couple thousandths smaller than your actual chamber.